Two types of bladed disks are known, one in which the blades are engaged in peripheral grooves in the disks, and another in which the disks are made integrally with the blades which are machined at the periphery of the disks (with disks of this type being referred to as one-piece bladed disks).
One-piece bladed disks are being used increasingly in the high pressure and low pressure compressors of turbojets, in order to reduce weight.
The various stages of disks can be assembled together axially by bolting, by electron beam welding, or, in particular when the disks are made of nickel alloy, by inertial or driven friction welding.
Friction welding consists in pressing a disk that is prevented from rotating hard against another disk that is rotating about its axis and that is prevented from moving in translation. The friction between the contacting faces of the disks gives off a large quantity of heat which raises the temperature of these faces that are in contact and enables them to be assembled together by welding.
Nevertheless, that assembly technique leads to intense levels of vibration and can cause the blades of one-piece bladed disks to be set into resonance, which can lead to them being destroyed by cracking due to vibratory fatigue.
As a result, friction welding is thus used only with disks having blades that are mechanically attached thereto subsequently, i.e. disks that present peripheral grooves for receiving and retaining the roots of blades.
One solution might be to assemble together one-piece bladed disks by friction welding before the blades have been machined so as to enable them to withstand vibration better, and then to machine the blades after the operation of welding the disks together. However that solution would be very expensive and risky, in particular because of the difficulties of using special tooling for machining blades between disks that have been assembled together.